Trailers of the type towed by vehicles, such as tractor trucks or semis and the like, in the trucking industry are typically equipped with one or more base axles upon which the trailer wheels are mounted so that the trailer is supported on a roadway or other surface. State bridge laws provide additional axle loads when the trailer features groups of axles that are spread apart by a specific distance. In response, spreader bars have been developed for use in the trucking industry. A “spreader bar” is a structural component that divides the base trailer axles and two or more auxiliary axles by a given distance.
A spreader bar typically permits the spreader axles to turn left or right about a vertical spreader pin, and with respect to the trailer, so that the trailer with the attached spreader bar and spreader bogie, to which the spreader axle and wheel assemblies are mounted, can successfully negotiate turns. In addition, the pitch of the spreader bar with respect to the trailer may typically be adjusted so that the portion of the load weight supported by the spreader axle and wheel assemblies may be adjusted. The pitch may be adjusted by mechanical shims, such as with a rigid spreader, or through the use of hydraulics, such as with a hydraulic spreader. A hydraulic spreader offers the advantages of finite and variable pitch adjustment and also allows rotation left to right and up and down, which reduces stress on the trailer and the vertical spreader pin.
Bridge laws vary from state to state. Some states allow more load per axle for specified spread distances measured from the last (most rearward) base axle of the trailer to the first axle of the spreader axles. Typical specified spread distances are 14′-7″ and 16′-1″. In order to change between these two distances, prior art systems require either an entirely new spreader bar or an alternative spreader main steering head assembly. Both of these solutions are expensive and time consuming with regard to installation.
A need exists for a hydraulic spreader bar that addresses the above issues and that reduces cost and time for change over.